Poly(p-hydroxy)styrenes, linear or branched, are available commercially and known in the art. For instance, U.S. Pat. No. 4,898,916 discloses the preparation of poly(vinylphenol) from poly(acetoxystyrene). U.S. Pat. No. 6,368,677, Hubbard et al, discloses a method for providing a waterborne, barrier coating to a polyolefin substrate. The method involves applying to the substrate a primer composition containing a commercial vinyl polymer derived from p-hydroxystyrene, wherein at least 75% of the polymer repeat units contain side groups having hydroxyl moieties. However, it would be desirable to have a polymer composition wherein the 4-acetoxystyrene, or an alkyl homolog, is incorporated at a low mol % as a random copolymer in a conventional thermoplastic polyolefin such as polyethylene. The presence of 4-acetoxystyrene or its hydrolyzed or transesterified form, 4-hydroxysytrene, may impart adhesive and compatibilizer properties not readily available in traditional polyolefin-based polymers. Such random modification to a polyethylene polymer should make these copolymers useful in a number of applications, including adhesion promoters, compatibilizers, and separation media.
Unexamined patent publication JP 1995220725 A discloses a copolymer of 70-99.99 mol % of aliphatic hydrocarbons monomers and ethylenically unsaturated monomers containing one or two carboxyl groups, anhydride or hydroxyl groups. A copolymer comprising 47.5 mol % ethylene, 47.5 mol % propylene and 5 mol % 4-hydroxystyrene is disclosed in Table 2 of the reference.
U.S. Pat. No. 4,748,209, Orikasa, et al, discloses a random copolymer of a styrene series monomer (including hydroxystyrene) and ethylene, wherein the content of the styrene monomer is within the range of 0.01 to 1.0 mol % (see, Col. 2, lines 63-68).
U.S. Pat. No. 4,182,803 and related U.S. Pat. No. 3,993,714, Kanagawa, et al, disclose a modified elastomer having a phenolic hydroxyl group on the side chain, obtained by copolymerizing at least one monomer selected from the group consisting of conjugated dienes, and monoethylenically unsaturated monomers, with a phenolic monomer including 3-hydroxystyrene and alkyl derivatives thereof. The disclosed group of polymers derived from monoethylenically unsaturated monomers includes monoolefins including ethylene. However, no copolymers specifically derived from the polymerization of ethylene and 3-hydroxystyrene or 4-hydroxystyrene are disclosed.
U.S. Pat. No. 6,001,532, Taylor, et al, disclose in claim 12 an organic layer comprising: structured block or random polymers prepared from at least one substituted styrene, including p-hydroxystyrene, and at least one other monomer, including ethylene. However, no copolymers specifically derived from the polymerization of ethylene and 3-hydroxystyrene or 4-hydroxystyrene are disclosed.
U.S. Pat. No. 4,039,630, Kanagawa, et al, discloses a modified elastomer having a phenolic hydroxyl group obtained by graft-copolymerizing an elastomer (derived from polymerization of ethylene, an α-olefin and at least one non-conjugated diene or polyene) with at least one vinyl phenolic monomer.
U.S. Pat. No. 6,759,483, Sheehan, et al, discloses a one-pot process for the preparation of homo-, co- and terpolymers of p-hydroxystyrene and alkyl acrylates. The process involves the polymerization of esters of p-hydroxystyrene, alkyl acrylates monomers and/or one or more of ethylenically unsaturated monomers in an alcohol solvent in the presence of a radical initiator. The so formed polymer is subjected to transesterification conditions using a catalytic amount of catalyst to provide co- and/or terpolymers of p-hydroxystyrene without cleavage of the alkyl ester in the acrylate repeat unit. This process is restricted to low pressure polymerizations, not compatible with the polymerization of ethylene copolymers.
Commonly owned U.S. patent application Ser. No. 11/135861 entitled “Method for making polyolefin graft polymers having improved adhesion properties” discloses the solution grafting of polyolefin polymers by grafting phenolic esters monomers, e.g. 4-acetoxystyrene, in the presence of radical initiator. The graft polymers provide useful adhesion promoters and compatibilizers. However, a polyolefin composition wherein the 4-acetoxystyrene was incorporated at a low mol % as a random copolymer, rather than a graft polymer, would be desirable.